Planographic printing plate material and planographic printing plate preparing process

Abstract

Disclosed are a planographic printing plate material and a planographic printing plate preparing process, the planographic printing plate material comprising a support and provided thereon, an image formation layer containing a colorant (a) having an absorption band in a wavelength region of from 700 to 1200 nm, a polymerization initiator (b) and a polymerizable ethylenically unsaturated compound (c), wherein the polymerization initiator (b) is a compound represented by the formula R 1 —CX 2 —(C═O)—R 2 .

What is claimed is: 
     
       1. A planographic printing plate material comprising a support and provided thereon, an image formation layer containing a colorant (a) having an absorption band in a wavelength region of from 700 to 1200 nm, a polymerization initiator (b) and a polymerizable ethylenically unsaturated compound (c), wherein the polymerizable ethylenically unsaturated compound (c) has a urethane bond in the molecule and wherein the polymerization initiator (b) is a compound represented by the following formula (1),
   R 1 —CX 2 —(C═O)—R 2   Formula (1)
 
 
       wherein R 1  represents a hydrogen atom, a bromine atom, or a chlorine atom; R 2  represents a hydrogen atom or a first monovalent organic substituent, provided that R 1  and R 2  may combine with each other to form a ring; and X represents a bromine atom or a chlorine atom. 
     
     
       2. The planographic printing plate material of  claim 1 , wherein R 2  represents —(Y)—R 3  in which Y represents an oxygen atom or —NR 4 — in which R 4  represents a hydrogen atom or an alkyl group, and R 3  represents a hydrogen atom or a second monovalent organic substituent. 
     
     
       3. The planographic printing plate material of  claim 1 , wherein the colorant is a cyanine dye. 
     
     
       4. The planographic printing plate material of  claim 1 , wherein the colorant is carbon black. 
     
     
       5. The planographic printing plate material of  claim 1 , wherein the image formation layer further comprises at least one compound selected from the group consisting of a sulfonium salt, a iodonium salt, an iron-arene compound and a titanocene compound. 
     
     
       6. The planographic printing plate material  claim 1 , wherein an overcoat layer containing polyvinyl alcohol as the main component is provided on the image formation layer. 
     
     
       7. A process of preparing a planographic printing plate, the process comprising the steps of imagewise exposing the planographic printing plate material of  claim 1  to laser having an emission wavelength of from 700 to 1200 nm, and developing the exposed planographic printing plate material with an alkali developer. 
     
     
       8. A process of preparing a planographic printing plate, the process comprising the steps of imagewise exposing the planographic printing plate material of  claim 6  to laser having an emission wavelength of from 700 to 1200 nm, washing the exposed planographic printing plate material with water to remove the overcoat layer, and developing the washed planographic printing plate material with an alkali developer.